1. Field of the Invention
Many types of industrial machinery have reciprocative or oscillatory mechanisms actuated pneumatically or by gravity or springs. A majority of such devices are operated by reciprocative pneumatic actuators, and in the main, the present disclosure describes problems involved in the use of such actuators and the solution of those problems. It is intended however that the use of the new improved hydraulic cartridges described herein not be limited to pneumatic actuators.
2. Description of the Prior Art Regarding Actuators
The usual reciprocative pneumatic actuator consists of a single cylinder with reciprocative piston and rod, the cylinder being closed at its ends by heads through which compressed air is supplied and exhausted. When compressed air enters the cylinder it tends to move the air piston so quickly and with such force that the piston and any moving load attached to it strike with heavy impact at the ends of the stroke. The impact resulting from an air piston striking the heads can be severe enough to damage the actuator and the mechanism driven by it. The impact can easily be great enough to shear off the mounting bolts of the actuator completely, thereby releasing the same from its base. The consequent danger to personnel and equipment is readily understandable, yet many pneumatic actuators are operated just as they are received from the seller, with no safeguarding against impact, so that direct impact of the piston against one or both of the heads often provides the only means of stopping the piston and its attached load. Such actuators must be operated at low speed at much less than their potential power output to save them from destruction. Operation at a safe low speed is usually accomplished by restricting the flow of air to or from the actuator, most pneumatic actuators being operated at speeds much lower than would be most economical for the moving load attached to them, because the operator adjusts the airflow low enough to be on the safe side. An expensive loss in efficiency occurs then because the full stroke of the air piston must be traveled at low speed, with consequent low productive capacity of the device.